The invention concerns a bellows device of the type comprising an elastic bellows adapted to be connected at a first end to a first rotary member and the second end of which is turned back axially outwards, the free end of the turned back portion being adapted to be fixed to a second rotary member.
The invention applies to constant velocity joints transmitting rotary movement between two shafts, in particular in automobile vehicles. Joints of this kind generally comprise a joint body attached to one of the shafts and surrounding a device transmitting rotary movement between the two shafts, for example a tripod device.
A bellows device is then connected to one of the shafts and to a cover extending the joint body attached to the second shaft in order to protect the transmission device against foreign bodies and to retain the lubricant therein.
When one of the shafts is rotated the bellows tends to move away from the first shaft because of centrifugal forces. The general arrangement of the aforementioned type of bellows device and in particular the turning back of the bellows holds the bellows near the first shaft and therefore limit the effect of such forces.
However, for high rotation speeds the outward movement of the bellows due to centrifugal forces can become sufficient to cause it to crease at the inside boundary where the free edge of its turned back portion is fixed to the cover.
Because of high rotation frequencies, this creasing lead to premature wear and to tearing of the bellows in the area of the crease. Problems of this kind are encountered in particular in constant velocity transmission joints operating in high-temperature and/or low-pressure environments (for example at high altitudes). In such cases the pressure inside the bellows is greater than the external pressure which encourages movement of the bellows away from the first shaft.
An aim of the invention is to provide a solution to the problems mentioned above and in particular to provide a bellows device capable of operating at high rotation speeds and in high-temperature or low-pressure environments with limited damage to the bellows.